noun
eternity; forever; very long period
Poetic or literary word for an extremely long time, often used in wishes for longevity or in traditional expressions. Not an everyday word for 'forever'.
君が代は千代に八千代にさざれ石の巌となりて苔のむすまで。
May your reign last for a thousand, nay, eight thousand generations, until pebbles grow into boulders and moss covers them.
noun
eight thousand years
Original literal meaning; now mainly encountered in classical contexts or as an etymological note.
八千代という言葉は、文字通りには八千年を意味する。
The word 八千代 literally means eight thousand years.
千代 means 'a thousand years' or 'eternity' and is more common than 八千代 in poetry and names.
From 八 (eight) + 千 (thousand) + 代 (generation/age), literally 'eight thousand generations', used hyperbolically to mean an immeasurably long time.